TextBlock binding not working - wpf

Question

I have a TextBlock that bind to property in my model. My model sitting in my view model that bind with the window.
<TextBlock Text="{Binding MyModel.TextVar,Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}"></TextBlock>
TextVar is a string property that call function of Notify...
So, I do not understand why it does not work. (There is no binding error in the OutPut).
EDIT:
string _textVar;
public string TextVar
{
get
{
return _textVar;
}
set
{
_textVar= value;
NotifyPropertyChanged("TextVar");
}
}
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)-- HERE THE PROPBLEM, IT ARRIVE NULL
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;

Answer 1

Seems that everything is perfect, now just add this line under the constructor of your class.
this.DataContext = this;
The problem arries when you have declared another DataContext in some parent window. I was suffering from same problem and this solution worked for me.
A Quick Review of Binding a TextBox in WPF
Step 1: Declare a property in class of window
first of all, you should declare a property in class of you window, i.e in .xml.cs file of your new window.
string _someVariable;
public string NameOfProperty
{
get
{
return _someVariable;
}
set
{
_someVariable= value;
}
}
Step 2: Bind the property to TextBox
Now bind your TextBox to your newly created property using the following syntax.
{Binding Path=NameOfProperty}
The Path notes the property that you want to bind to, however, since Path is the default property of a binding, you may leave it out if you want to, like this:
{Binding NameOfProperty}
Step 3: Declare the DataContext of your Window
Your solution should work until now, but in case you are using some pattern you should define the DataContext of your window.

Answer 2

Binding TextBlock with Mode=TwoWay makes no sense because its a TextBlock and not a TextBox.
but nevertheless your binding work if the DataContext of your textblock has a Property "MyModel" and this "MyModel" - object has a Property "TextVar".
if you wanna look up your datacontext and binding at runtime use Snoop
EDIT: that what you need if you do your binding like you did
public class MyViewmodel
{
public MyOtherClass MyModel {get;set;}
}
public class MyOtherClass
{
public string TextVar {get;set;}
}
windows.xaml.cs ctor:
this.data = new MyViewmodel();
this.DataContext = this.data;